Method of blade construction



Aug. 2, 1960 J, w. TU MAvlcus 2,947,066

I METHOD 0F BLADE CONSTRUCTION Filedmay 8, 195'? l /6 l ,6 I 6 F JZ INVENTOR. daawl/rz/mv/cw L- BY JLA United States Patent() 2,947,066 METHOD F BLADE CONSTRUCTION Julius William Tumavicus, 01d Saybrook, Conn., assignor to the United States of America as represented by the Secretary of the Air Force Filed May 8, 1957, Ser. No. 657,983

3 Claims. (C1. 294-1565) This invention relates to rotor blades for turbines, compressors, blowers or the like, and is more particularly concerned with an improved method of making such blades.

One of the conventional manners in which a blade is mounted on the rotor disc is by means of a pin which passes through an aperture formed in the shank of the blade. It has been found that the methods now used for forming the hole in such av blade result in production of a member which exhibits structural weakness and metal strain at the mounting end. This deficiency causes short operating life in the rotor, andv it can also cause dangerous accidents should the blade come loose during rotation.

Therefore, it is a primary object of this invention to provide a new and improved method of forming rotor' blades which method will substantially eliminate present shortcomings.

A further object of the invention is to provide such an improved method while still producing an inexpensive blade which is not undesirably heavy.

The above and still further objects of the invention will become apparent upon consideration of the following detailed description thereof, especially when taken in conjunction with the accompanying drawings, in which:

Figure l shows a rotor blade as it appears when blanked from sheet stock;

Figure 2a shows said blade with ears formed thereon;

Figure 2b shows the blade in an intermediate wrapping step;

Figure 3 shows said blade as iinally wrapped around the pin hole insert;

Figure 4 is a sectional view of the securing platform taken on the line IV-IV of Figure 5;

Figure 5 is a top view of the blade as assembled; and

Figure 6 is a side view of the blade in Figure 5.

In the drawings like characters of reference indicate like parts. In the first step of my invention a piece of sheet stock is blanked to the shape shown in Figure l. 'Ihe diametrically opposed ends 10 and 12 will hereinafter be referred to as blade portions, and the central segment 14 will be referred to as the base or root vportion. After the blanking operation, the blade portions and 12 are each coined to a half airfoil contour. The coining is such that when the entire member is folded around the base or root portion 14, the flat faces of said blade portions will come into contact with each other whereby their overall contour is of full airfoil shape. As is known inthe art such a shapeiis designed to provide minimal resistance to flow.

After coining, the root portion 114 is formed with two pairs of transition ears 16 and 18 by a similar blanking. Said pairs are positioned with one ear on each lateral edge of portion 14, and are separated longitudinally by a smooth central segment 20.

2,947,066 Patented Aug. 2, 1960 ICC The blade portions 10 and 12 are now folded toward each other, the segment 20 forming a center point as seen in Figure 2b. As the at faces of the airfoil contours approach each other, the ears 16 and 18 are also coming together. Prior to the point at which4 such members actually do come together, a pin hole insert 22 is positioned within an opening 24 formed between the inner ends of the ears '16 and 18. With insert 22 in place, the folding process continues until the structure of Figure 3 is reached. Here the ears are in contact, and with segment 20, are wrapped completely around the periphery of the insert 22. The -hole formed in said insert is adapted to receive a pin for attachment to the rotor. By using such a separate insert, said pin hole can easily be positioned at a point wherein the least amount of stress is exerted.

A platform 26 is placed at the junction of the ears and the blade portions. This serves to secure and strengthen the blade. The entire assembly is then furnace brazed, and a finished rotor blade, ready for use, results.

It is to be understood that the above-described embodiment is merely illustrative of the principles of my invention. Various changes and modifications may be made therein by those skilled in the art without departing from the spirit and scope thereof.

What is claimed is:

1. A method of forming rotor blades for turbines, compressors, blowers and the like: said method comprising the steps of blanking sheet stock to have a pair of blade portions separated by a 'relatively narrower base portion; coining each of said blade portions to half airfoil contour; blanking a pair of ears on the lateral edges of said base portion adjacent each of said blade portions, each of said ears tapering from an apex at the junction of said ear with the blade portion; folding said blade portions toward each other so that the flats of said half arfoil contours approach each other; inserting a member having a pin receiving hole into an opening formed by said base portion and said ears; continuing folding until said ats and the said ears proximate to the opposed ilats of said blade portions are in contact; brazing the assembled parts.

2. A method as dened in claim 1, and including the step of strengthening the junction of said ears and said blade portions by positioning o'f a platform at said junction prior to brazing.

3. A method of forming rotor blades for turbines, compressors, blowers and the like which comprises the steps of blanking a piece of sheet stock to form a pair of blade portions, a central portion narrower than said blade portions, and tapering sections joining said central portions to said blade portions, blanking ears tapering from the blade portion to a maximum dimensioned portion adjacent the said central portion on the lateral edges of each of said tapering sections, folding said blade portions and tapering sections toward each other, inserting a pin hold member in the opening formed by said tapering sections and said central portion, continuing said folding until said blade portions and said ears adjacent opposed edges of said blade portions are in contact and said maximum dimensioned portion and said central portion encompass said pin hold member, and subjecting the parts so assembled to linish brazing.

References Cited in the file of this patent UNITED STATES PATENTS 

